Date: Mon, 22 Sep 2003 17:26:02 +0100
From: Jamie Lokier <jamie@shareable.org>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Can we kill f inb_p, outb_p and other random I/O on port 0x80, in 2.6?
Message-ID: <20030922162602.GB27209@mail.jlokier.co.uk>
References: <m1isnlk6pq.fsf@ebiederm.dsl.xmission.com> <1064229778.8584.2.camel@dhcp23.swansea.linux.org.uk>
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Alan Cox wrote:
> (one part of the problem of course is you need inb_p/outb_p to drive
> the timer chip on some x86 boards in order to calibrate the udelay
> timer)

What sort of timer chip problems do you see?  Is it something that can
be auto-detected, so that timer chip accesses can be made faster on
boards where that is fine?

I'm sure I've seen timer chip code in DOS programs that didn't have
the extra delay I/Os.  Surely it cannot be a very widespread problem.

> > When debugging this I modified arch/i386/io.h to read:
> > #define  __SLOW_DOWN_IO__ ""
> > Which totally removed the delay and the system ran fine.
> 
> Not all systems do - we had breakages from both the keyboard controller
> and the timer chips even on some modern boards when this got messed up.

I've also seen much DOS code that didn't have extra delays for
keyboard I/Os.  What sort of breakage did you observe with the
keyboard?

Thanks,
-- Jamie
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